Search-light reflector.



M. VON Rom. SEARCH LIGHT REFLECTOR. APPLICATION FILED MAY 8, 1906.

Patented Nov. 10,1908.

tween the double paraboli am MORITZ VON ROHR, OF

JENA, GERMANY, ASSIGNOR'TO THE GERMANY.

FIRM OF CARL ZEISS, OF IENA,

SEARCH-LIGHT REFLECTOR.

No. 903,32i.

Specification of! Letters Patent.

Patented Nov. 10, 1908.-

Application filed May 8, 1906. .Serial No. 316,753.

To of! whom it may concern:

Brit known that I, uonrrz VON ROI-IR, l doctor of philosophy, a citizen of the Gerl man Empire, and residing at Carl-Zeiss strasse, Jena, in the Grand Duchy of Saxo- Veim ar, Germany, have invented a new and useful Searcl'f-Light Reflector, of which the following is a specification.

Hollow reflectors for search lights are now almost exclusively manufactured as glass bodies, which are of lens configuration, their limiting, optically operative, surfaces being coaxial surfaces of revolution and the outer (convex) lens surface silvered. Two kinds of such reflectors are known. in one, hereafter called the spherical one, both surfaces of revolution are s )hrrical and designed so that 1 the lens akes the form of a negative 1 .\enis cus. Those l't'llOflUlS possess, as is known, '5 thigreat morit, that their surfaces, being s ihl-riral, are easily produced. The design also allows these two surfaces to be deter mined so that no greater spherical ahcrration m-eurs, between any rays entering the. lens parallel to the axis, than is admissible l for a search light reflector u'it-hregard to the Z lninimum diameter of the source of light. A sensible disadvantage of the spherical reflr-ctor consists in the great increase of the thickness from the vertex towards the margin. This reflector frequently suffois from cracks in consequence of unequal hcatim, in

the mass by the source of light. The second kind of hollow glass search light reflector displays two parabolic surfaces of revolution. it is fairly free from the defect of unequal thickness, but in comparison to the spherical reflector it has the dram-bark, that the manu 1 'facture of the two operative surfaces presents greater difficulty. l The present. invention consists in a third l kind of hollow glass reflector-for search lights. I This new reflector possesses a more evonl thickness than the spherical one. If.- permils of the reduction of the spherical abcrration even to a still grealrmlegroe, or its total elimination. As regards the difficulty of j inamifaethre it occupies a mean iosilion hrl the spherical reflectors. in order to realize these eonditions let a r flector be'sup )osed, whose inii tial operative surfaces of revolution are spherical but differing, from those of lhei heriral reflector above referred to in that I ey are nearly or exactly concentric, and

would be attained,

whose thickness consequently displays no rcat difference, or is even everywhere equal. The gross spherical aberration, the inherent property of such a reflector, is eliminated by suitably deforming the inner or outer spherical surface, so that it gives place to a nonspherical surface of revolution. The meridian curve of a surface deformed to counteract the above mentioned aberration can be ascertained not only by calculation but also empirically by carrying out the deformation on a double spherical initial form zonewiseand testing the optical effect zonewise. The calculation of the deformed surface is preferably begun at the vertex, and in addition to the curvature of the s lterical surface, the thickness at the vertex of the reflector together with the curvature of the vertex of the deformed surface chosen the focal length of the reflector being thereby determined.

By the vertex value of curvature of the meridian curve of the non-spherical surface, hereafter called the curvature. of the vertex, an ideal spherical surface with the same vertex is determined, spherical surface must deviatein order to counteract the spherical aberration of the reircction awa' from the real spherical corfloctor--in the 1 .--.pheri :al surface. rect-ion up to the curvature of the meridiancurve of the non-sphericalsurface should decrease or increase constantly from the vertex to.thc margin, according as the outer (reflecting) or the inner surface is'bcing deformed. From this it follows that the thickness of the reflector steadily increases up to the margin-though in much lesser degree than in the spherical rellector---if the curvature of the vertex he 95 chosen so as to make the ideal spherical surface concentric to the real spherical surface. In order to obtain a still more uniform thickness of the reflector, with good spherical correction throughout, the

the ideal spherical surface) should be smaller, in delormation of the inner surface, and larger, in deformation of the outer, than the curvature of another ideal spherical sur- 105 from which the nonthe margin of the reflector (reflecting) I rule must be observed that the curvature of the vertex (of drawing: Figure l is an axial sect it) through a reflector splicric- 10 ally corrected according to the invention. Fig. 2 is a similar section through another relector spherically corrected according to the invention.

The reflector shown in Fig. 1 has. the inner surface '5 deformed. The vertex radius r of this non-spherical surfacebeing at the same'tiine the radius of the ideal spherical surface i is greater than the radius r 'of the real spherical surface e, so that the surface t deviates from another idral'spherical'surface (which could not be repnese. ted in the..draw'- ing) having the same vertex and a radius r,-d, towards the surface 0. The radius vectorR' drawn from that point of the axis 8, which is the terminal point of the vertex radius 1' to the nonspherical surface 2' decreases continuously with increasin vectorial angle 0, the surface i deviating rom the surface 11 in the direction away from the surface 6. The thickness of the reflector decreases slowly fromthe vertex value (1 out:

wards, until it reaches a minimum near. the

margin, whereafter it increases more rapidly. up to the margin. The half angle of aperture- The. reflector shown in Fig. 2 has the outer surface e deformed. The vertex radius r, of thisnon-spherical surface (the radius of the ideal spherical surface e is smaller than the radius r, of the real spherical surface 2'. Hence the surface 6 deviates towards the A surface 1' from an ideal spherical surface passe.-

through the vertex of e and e and having radius r,+d. The 1 :adius vector R drawn from the terni/ilnalpoint of the vertex radius -r to the non-spherlc'alsur ace increases con- -t uously with the vectorial angle 0, the surface e deviating from the surface e in the direction away from the surface-i. .The thickness of the reflector, as in the example shown in 1, decreases slowly from the value d surface, in the direction awa at the vertex outwards, reaches a minimum near the mar in and then increases more rapidly up to t 1e margin.- aperture u is 59.

What I claim as my invention, and desire to secure by Letters Patent, is

v A hollow glass reflector for search lights and the like, limited by two coaxial surfaces of revolution, an exterior. reflecting surface and an interior refracti'n surface, one of these surfaces bein spherical and the other non-spherical, the fatter deviatingfor the purpose of'counteractin the spherical abe'1' and an interior refracting surface of revolution, these surfaces being coaxial to each one of them being spherical and the other, other non-spherical, the non-spherical surface deviatin froma coaxial spherical-ideal surface, whici passes throu h, and has the curvature of, the vertex of the non-spherical from the real slpherical surface, and the said ideal surface eviatin from another coaxial spherical ideal sur? face, in the direction towards t face.

In testimony whereof have is real surtwo subscribing witnesses.

MORITZ VON ROHR. Witnesses:

PAUL KRi'JoER,

FRITZ SANDER.

The half angle of 45 ace, passing through the same ver- 7 -tex, but concentric to the real s herical sur- I signed my name to thls specificatlon in the presence of 

